Add sanity checks for input string in wxHexToDec()

Check if the length of the string is appropriate and if it contains hexadecimal characters.
Also document this function.

Closes #12814.

include/wx/utils.h

@@ -296,15 +296,23 @@ inline int wxHexToDec(const char* buf)
 
     if (buf[0] >= 'A')
         firstDigit = buf[0] - 'A' + 10;
-    else
+    else if (buf[0] >= '0')
         firstDigit = buf[0] - '0';
+    else
+        firstDigit = -1;
+
+    wxCHECK_MSG( firstDigit >= 0 && firstDigit <= 15, -1, wxS("Invalid argument") );
 
     if (buf[1] >= 'A')
         secondDigit = buf[1] - 'A' + 10;
-    else
+    else if (buf[1] >= '0')
         secondDigit = buf[1] - '0';
+    else
+        secondDigit = -1;
 
-    return (firstDigit & 0xF) * 16 + (secondDigit & 0xF );
+    wxCHECK_MSG( secondDigit >= 0 && secondDigit <= 15, -1, wxS("Invalid argument") );
+
+    return firstDigit * 16 + secondDigit;
 }
 
 

interface/wx/utils.h

@@ -1474,4 +1474,25 @@ wxString wxDecToHex(unsigned char dec);
     @header{wx/utils.h}
 */
 void wxDecToHex(unsigned char dec, char* ch1, char* ch2);
+
+/**
+    Convert 2-character hexadecimal string to decimal integer.
+
+    @param buf
+        String containing uppercase hexadecimal characters, not prefixed
+        by @c 0x. Its length must be at least 2 characters. If it is longer
+        than 2 characters, only first two will be converted to the number.
+
+    @return
+        An integer number between 0 and 255 that is equivalent to the number
+        in @a buf, or @c -1 if @a buf is not a hexadecimal string.
+
+    @header{wx/utils.h}
+*/
+int wxHexToDec(const wxString& buf);
+
+/**
+    @overload
+*/
+int wxHexToDec(const char* buf);
 //@}

src/common/utilscmn.cpp

@@ -122,10 +122,12 @@ static const char hexArray[] = "0123456789ABCDEF";
 // Convert 2-digit hex number to decimal
 int wxHexToDec(const wxString& str)
 {
+    wxCHECK_MSG( str.Length() >= 2, -1, wxS("Invalid argument") );
+
     char buf[2];
     buf[0] = str.GetChar(0);
     buf[1] = str.GetChar(1);
-    return wxHexToDec((const char*) buf);
+    return wxHexToDec(buf);
 }
 
 // Convert decimal integer to 2-character hex string (not prefixed by 0x).